Photographic products and processes

ABSTRACT

Diffusion transfer photographic products comprising a support carrying at least two selectively sensitized silver halide emulsion layers, each having a dye which is a silver halide developing agent of predetermined color associated therewith, and a layer intermediate the emulsion layers comprising a processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming materials substantially only in the hydrated state.

Continuation-impart of application Ser. No. 486,862, Sept. 13, 1965, now abandoned which is a continuation-in-part of application Ser. No. 450,305, Apr. 23, 1965, now abandoned [54] PHOTOGRAPHIC PRODUCTS AND PROCESSES 32 Claims, 1 Drawing Fig.

[52] U.S.Cl 96/3,

[51] lnt.Cl G030 7/00, G03c 5/54, G03c 1/40, [50] Field of Search 96/3, 29 D;

[56] References Cited UNITED STATES PATENTS 3,325,283 6/1967 Barstow et al. 96/3 3,345,163 l0/l967 Land et al 96/3 Primary Examiner-Norman G. Torchin Assistant ExaminerAlfonso T. Suro Pico Attorneys-Brown & Mikulka, Sheldon W. Rothstein. Brown and Mikulka and Sheldon W. Rothstein ABSTRACT: Diffusion transfer photographic products comprising a support carrying at least two selectively sensitized silver halide emulsion layers, each having a dye which is a silver halide developing agent of predetermined color associated therewith, and a layer intermediate the emulsion layers comprising a processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming materials substantially only in the hydrated state.

-SUPPORT L CYAN DYE DEVELOPER LAYER RED SENSITIVE SILVER HALIDE EMULSION LAYER 'NTERWER -MAGENTA DYE DEVELOPER LAYER GREEN SENSITIVE SID/ER HALIDE EMULSION LAYER INTERLAYER VYELLOW DYE DEVELOPER LAYER BLUE SENSITIVE SILVER HALIDE EMULSION LAYER -OVERCOAT LAYER AQUEOUS ALKALINE PROCESSING COMPOSITION 2| --lMAGE-RECEIVING LAYER NEUTRALIZING LAYER SUPPORT PATENTEDUET 2s IHTI SUPPURT F CY DYE UEWELOPER LAYER RED SENSITWE SLLVE LHDE EMULSRON LAYER &\\\\\\\\\\\\ 7////////////;*

-nmsmm -MAGENTA DYE DEVELOPER LAYER &\\\\\\\\\\\\ EM 3 ON GREEN SENSH'WE SELVER HALIDE UL I LAYER VYELLQW DYE DEVELQPER LAYER ////////////7{Eb%iiSL ER AQUEOUS LIKMUNE PRQQESSKW COPOSWLUN EMAGE- ECEWBE LYE PEUTHALMH LYE Pliilfit'llUGhAlPllilliC lfliifilli ilfl'lld AND lFlMltfIlESSEh This application is a continuation-in-part of copending U.S. application Ser. No. 486,862, filed Sept. 13, I965, now abancloned which is in turn a continuation-in-part of U.S. application Scr. hlo. 450,305, filed Apr. 23, I965, and now abancloned.

The present invention relates to photography and, more particularly, to photographic products particularly adapted for employment in photographic diffusion transfer color processes.

The primary objects of the present invention are to provide photographic products, particularly adapted for employment in diffusion transfer photographic color processes; to provide photographic products which include a photosensitive element which comprises a plurality of essential layers including, superposed on a common support, at least two selectively sensitized photosensitive strata each having associated therewith, as color transfer image-forming components, a dye of predetermined color which is a silver halide developing agent, wherein at least two of said sensitized strata and associated dyes are separated from each other by a layer comprising a synthetic, metal-free polymer as specified hereinafter; to provide photographic diffusion transfer products comprising a photosensitive element, of the last-identified type, in combination with a photographic diffusion transfer image-receiving element comprising a plurality of essential layers including a common support carrying a solution dyeable polymeric layer; and to provide photographic diffusion transfer color processes employing photosensitive film units including, in combination, a photosensitive element and a transfer image-receptive element of the last-identified type, and a fluid photographic transfer processing composition.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, the others and the relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description talren in connection with the accompanying drawing, wherein the FiGURlE detailed is a diagrammatic enlarged cross-sectional view illustrating the association of element during one stage of the performance of a diffusion transfer process, for the production of a multicolor positive transfer print, the thickness of the various materials being exaggerated.

As disclosed in US. Pat. No. 2,983,606, issued May 9, 1961, a photosensitive element containing a dye developer, that is, a dye which is a silver halide developing agent, and a silver halide emulsion may be exposed and wetted by a liquid processing composition, for example, by immersion, coating, spraying, flowing, etc., in the dark, and the exposed photosensitive element is superposed prior to, during, or after wetting, on a sheetlilte support element which may be utilized as an image-receiving element. In a preferred embodiment, the liquid processing composition is applied to the photosensitive element in a substantially uniform layer as the photosensitive element is brought into superposed relationship with the image-receiving layer. The liquid processing composition, positioned intermediate the photosensitive element and the image-receiving layer, permeates the emulsion to initiate development of the latent image contained therein. The dye developer is immobilized or precipitated in exposed areas as a consequence of the development of the latent image. This immobilization is apparently, at least in part, due to a change in the solubility characteristics of the dye developer upon oxidation and especially as regards its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidised developing agent, and in part to a localized exhaustion of alkali as a result of development. In unexposed and partially exposed areas of the emulsion, the dye developer is unreacted and diffusible and thus provides an imagewise distribution of unoxidized dye developer dissolved in the liquid processing composition, as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer or element, said transfer substantially excluding oxidized dye developer. The imageqeceiving element receives a depthwise diffusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewise distribution thereof to provide the reversed or positive color image of the developed image. The image-receiving element may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer. In one preferred embodiment, the desired positive image is revealed by stripping the image-receiving layer from the photosensitive element at the end of a suitable inhibition period.

The dye developers, as noted above, are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By "a silver halide developing function" is meant a grouping adapted to develop exposed silver halide. A preferred silver halide development function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. in general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

Multicolor images may be obtained using color image-form ing components such as, for example, the previously mentioned dye developers, in diffusion transfer processes by several techniques. One such technique contemplates obtaining multicolor transfer images utilizing dye developers by employment of an integral multilayer photosensitive element, such as is disclosed in the aforementioned US. Pat. No. 2,983,606, and particularly with reference to FIG. 9 of the patents drawing, wherein at least two selectively sensitized photosensitive strata, superposed on a single support, are processed, simultaneously and without separation, with a single, common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide stratum, a green-sensitive silver halide emulsion stratum and a blue-sensitive silver halide emulsion stratum, said emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. The dye developer may be utilized in the silver halide emulsion layer, for example, in the form of particles, or it may be employed as a layer behind the appropriate silver halide emulsion strata. Each set of silver halide emulsion and associated dye developer strata are disclosed to be optionally separated from other sets by suitable interlayers, for example, by a layer of gelatin or polyvinyl alcohol. In certain instances, it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable, a yellow dye developer of the appropriate spectral characteristics and present in a state capable of functioning as a yellow filter may be employed. In such instances, a separate yellow filter may be omitted.

The dye developers are dye image-forming materials which are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, that is, the previously mentioned cyan, magenta and yellow. The dye developers employed may be incorporated in the respective silver halide emulsion or, in the preferred embodiment in a separate layer behind the respective silver halide emulsion. Specifically, the dye developer may, for example, be in a coating or layer behind the respective silver halide emulsion and such a layer of dye developer may be applied by use of a coating solution about 0.5 to 8 percent, by weight, of the respective dye developer distributed in a film-forming natural, or

synthetic, polymer, for example, gelatin, polyvinyl alcohol, and the like, adapted to be permeated by the chosen diffusion transfer fluid processing composition.

An extensive compilation of specific dye developers particularly adapted for employment in photographic diffusion transfer processes is set forth in aforementioned U.S. Pat. No. 2,983,606 and in the various copending U.S. applications referred to in that patent, especially in the table of U.S. applications incorporated by reference into the patent as detailed in column 27. As examples of additional U.S. patents detailing specific dye developers for photographic transfer process use, mention may also be made of U.S. Pat. Nos. 2,983,605; 2,992,106; 3,047,386; 3,076,808; 3,076,820; 3,077,402; 3,126,280; 3,131,061; 3,134,762; 3,134,765; 3,135,604; 3,135,605; 3,135,606; 3,135,734; 3,141,772; 3,142,565; and the like.

As additional examples of synthetic, film-forming, permeable polymers particularly adapted to retain dispersed dye developer, mention may be made of nitrocarboxymethyl cellulose, as disclosed in U.S. Pat. No. 2,992,104; an acylamidobenzene sulfo ester of a partial sulfobenzal of polyvinyl alcohol, as disclosed in U.S. Pat. No. 3,043,692; polymers of N-alkyl-a,fi-unsaturated carboxamides and copolymers of N-alkyl-a,B-carboxamides with N-hydroxyalkyl-a,B-unsaturated carboxamides, as disclosed in U.S. Pat. No. 3,069,263; copolymers of vinyl-phthalimide and a,}3-unsaturated carboxylic acids, as disclosed in solvent, Pat. No. 3,061,428; copolymers of N-vinylpyrrolidones and a,B-unsaturated carboxylic acids, as disclosed in U.S. Pat. No. 3,061,428; copolymers of N-vinylpyrrolidones and B, fi-unsaturated carboxylic acids and terpolymers of N-vinyl-pyrrolidones, a,fl-unsaturated carboxylic acids and alkyl esters of a,B-unsaturated carboxylic acids, as disclosed in U.S. Pat. No. 3,044,873; copolymers of N,N-dialkyl-a,B-unsaturated carboxamides with a,fi-unsaturated carboxylic acids, the corresponding amides of such acids, and copolymers of Naryland N-cycloalkyl-a,fi-unsaturated carboxamides with a,B-unsaturated carboxylic acids, as disclosed in U.S. Pat. No. 3,069,264; and the like.

In addition to conventional techniques for the direct dispersion of a particulate solid material in a polymeric, or colloidal, matrix such as ball-milling and the like techniques, the preparation of the dye developer dispersion may also be obtained by dissolving the dye in an appropriate solvent, or mixture of solvents, and the resultant solution distributed in the polymeric binder, with optional subsequent removal of the solvent, or solvents, employed, as, for example, by vaporization where the selected solvent, or solvents, possesses a sufficiently low boiling point or washing where the selected solvent, or solvents, possesses a sufficiently high differential solubility in the wash medium, for example, water, when measured against the solubility of the remaining composition components, and/or obtained by dissolving both the polymeric binder and dye in a common solvent.

For further detailed treatment of solvent distribution systems of the types referred to above, and for an extensive compilation of the conventional solvents traditionally employed in the art to effect distribution of photographic colorproviding materials in polymeric binders, specifically for the formation of component layers of photographic film units, reference may be made to U.S. Pat. Nos. 2,269,158; 2,322,027; 2,304,939; 2,304,940; 2,801,171; and the like.

U.S. Pat. No. 3,362,819 discloses image-receiving elements, particularly. adapted for employment in the preceding diffusion transfer processes, which comprise a support layer possessing on one surface thereof, in sequence, a polymeric acid layer, preferably an inert timing or spacer layer, and an imagereceiving layer adapted to provide a visible image upon transfer to said layer of diffusible dye image-forming substance.

As set forth in the last-mentioned patent, the polymeric acid layer comprises polymers which contain acid groups, such as carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals, such as sodium potassium, etc., or with organic bases, particularly quaternary ammonium bases, such as tetramethyl ammonium hydroxide, or potentially acid-yielding groups, such as anhydrides or lactones, or other groups which are capable of reacting with bases to capture and retain them. The acid-reacting group is, of course, nondiffusible from the acid polymer layer. In the preferred embodiments disclosed, the acid polymer contains free carboxy groups and the transfer processing composition employed contains a large concentration of sodium and/or potassium ions. The acid polymers stated to be most useful are characterized by containing free carboxyl groups, being insoluble in water in the free acid form, and by forming watersoluble sodium and/or potassium salts. One may also employ polymers containing carboxylic acid anhydride groups, at least some of which preferably have been converted to free carboxyl groups prior to imbibition. While the most readily available polymeric acids are derivatives of cellulose or of vinyl polymers, polymeric acids from other classes of polymers may be used. As examples of specific polymeric acids set forth in the application, mention may be made of dibasic acid halfester derivatives of cellulose modified with sulfoanhydrides, e.g., with ortho-sulfobenzoic anhydride; polystyrene sulfonic acid; carboxymethyl cellulose; polyvinyl hydrogen phthalate; polyvinyl acetate hydrogen phthalate; polyacrylic acid; acetals of polyvinyl alcohol with carboxy or sulfo-substituted aldehydes, e.g., o-, m-, or p-benzaldehyde sulfonic acid or carboxylic acid; partial esters of ethylene/maleic anhydride copolymers; partial esters of methyl-vinyl ether/maleic anhydride copolymers; etc.

The acid polymer layer is disclosed to contain at least sufficient-acid groups to effect a reduction in the pH of the image layer from a pH of about 13 to 14 to a pH of at least 11 or lower at the end of the imbibition period, and preferably to a pH of about 5 to 8 within a short time after imbibition. As previously noted, the pH of the processing composition preferably is of the order of at least 13 to 14.

It is, of course, necessary that the action of the polymeric acid be so controlled as not to interfere with either development of the negative or image transfer of unoxidized dye developers. For this reason, the pH of the image layer is kept at a level of pH 12 to 14 until the positive dye image has been formed, after which the pH is reduced very rapidly to at least about pH 1 1, and preferably about pH 9 to 10, which renders unoxidized dye developer substantially nondiffusible. Unoxidized dye developers containing hydroquinonyl developing radicals diffuse from the negative to the positive as the sodium or other alkali salt. The diffusion rate of such dye image-forming components thus is at least partly a function of the alkali concentration, and it is necessary that the pH of the image layer remain on the order of 12 to 14 until transfer of the necessary quantity of dye has been accomplished. The subsequent pl-l reduction, in addition to its desirable effect upon image light stability, serves a highly valuable photographic function by substantially terminating further dye transfer.

In order to prevent premature pH reduction during transfer processing, as evidenced, for example, by an undesired reduction in positive image density, the acid groups are disclosed to be so distributed in the acid polymer layer that the rate of their availability to the alkali is controllable, e.g., as a function of the rate of swelling of the polymer layer which rate in turn has a direct relationship to the diffusion rate of the alkali ions. The desired distribution of the acid groups in the acid polymer layer may be effected by mixing the acid polymer with a polymer free of acid groups, or lower in concentration of acid groups, and compatible therewith, or by using only the acid polymer but selecting one having a relatively lower proportion of acid groups. These embodiments are illustrated, respectively, in the cited patent by (a) a mixture of cellulose acetate and cellulose acetate hydrogen phthalate and (b) a cellulose acetate hydrogen phthalate polymer having a much lower percentage of phthalyl groups than the first-mentioned cellulose acetate hydrogen phthalate.

it is also disclosed that the layer containing the polymeric acid may contain a water insoluble polymer, preferably a cellulose ester, which acts to control or modulate the rate at which the alkali salt of the polymer acid is formed. As examples of cellulose esters contemplated for use, mention is made of cellulose acetate, cellulose acetate butyrate, etc. The particular polymers and combinations of polymers employed in any given embodiment are, of course, selected so as to have adequate wet and dry strength and when necessary or desirable, suitable subcoats may be employed to help the various polymeric layers adhere to each other during storage and use.

The inert spacer layer of the aforementioned patent, for example, an inert spacer layer comprising polyvinyl alcohol or gelatin, acts to time" control the pH reduction by the polymeric acid layer. This timing is disclosed to be a function of the rate at which the alkali diffuses through the inert spacer layer. It was stated to have been found that the pH does not drop until the alkali has passed through the spacer layer, i.e., the pH is not reduced to any significant extent by the mere diffusion into the interlayer, but the pH drops quite rapidly once the alkali diffuses through the spacer layer. Other such spacer layers which are suitable for use in the image-receiving element are disclosed and claimed in U.S. Pat. No. 3,421 ,893.

As examples of materials for use as the image-receiving layer, mention may be made of solution dyeable polymers such as nylons as, for example, N-methoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; cellulose acetate with fillers as, for example, one-half cellulose acetate and one-half oleic acid; gelatin; and other materials of a similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in U.S. Pat. No. 3,148,061.

As disclosed in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for example, diethylamine, sodium hydroxide or sodium carbonate and the like, and preferably possessing a pH in excess of 12, and most preferably, a viscosity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, forms a relatively firm and relatively stable film. The preferred film'forming materials disclosed comprise high molecular weight polymers such as polymeric, water-soluble ethers which are inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Additionally, film-forming materials or thickening agents whose ability to increase viscosity is substantially unaffected if left in solution for along period of time are also disclosed to be capable of utilization. As stated, the film-forming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of 100 c.p.s. at a temperature of approximately 24 C. and preferably in the order of 100,000 c.p.s. to 200,000 c.p.s. at that temperature.

For the production of the photoresponsive gelatino silver halide emulsions employed to provide the film unit, the silver halide crystals may be prepared by reacting a water-soluble silver salt, such as silver nitrate, with at least one water-soluble halide, such as ammonium, potassium or sodium bromide, preferably together with a corresponding iodide, in an aqueous solution of a peptizing agent such as a colloidal gelatin solution; digesting the dispersion at an elevated temperature, to provide increased crystal growth; washing the resultant dispersion to remove undesirable reaction products and residual water-soluble salts by chilling the dispersion, noodling the set dispersion, and washing the noodles with cold water, or, alternatively, employing any of the various flocc systems, or procedures, adapted to effect removal of undesired components, for example, the procedures described in U.S. Pat. Nos. 2,614,928; 2,614,929; 2,728,662; and the like; afterripening the dispersion at an elevated temperature in com bination with the addition of gelatin and various adjuncts, for

example, chemical sensitizing agents of U.S. Pat. Nos. 1,574,944; 1,623,499; 2,410,689; 2,597,856; 2,597,915; 2,487,850; 2,518,698; 2,521,926; and the like; all according to the traditional procedures of the art, as described in Neblette, C. B, Photography Its Materials and Processes, 6th Ed, 1962.

Optical sensitization of the emulsion's silver halide crystals may be accomplished by contact of the emulsion composition with an effective concentration of the selected optical sensitizing dyes dissolved in an appropriate dispersing solvent such as methanol, ethanol, acetone, water, and the like; all according to the traditional procedures of the art, as described in Hammer, 1F. ML, The Cyanine Dyes and Related Compounds.

Additional optional additives, such as coating aids, hardeners, viscosity-increasing agents, stabilizers, preservatives, and the like, for example, those set forth hereinafter, also may be incorporated in the emulsion formulation, accord ing to the conventional procedures known in the photographic emulsion manufacturing art.

The photoresponsive material of the photographic emulsion will, as previously described, preferably comprise a crystal of silver, for example, one or more of the silver halides such as silver chloride, silver iodide, silver bromide, or mixed silver halides such as silver chlorobromide or silver iodobromide, of varying halide ratios and varying silver concentrations.

The emulsions may include the various adjuncts, or addenda, according to the techniques disclosed in the art.

As the binder for the respective emulsion strata, the aforementioned gelatin may be, in whole or in part, replaced with some other colloidal material such as albumin; casein; or zein; or resins such as a cellulose derivative, as described in U.S. Pat. Nos. 2,322,085 and 2,327,808; polyacrylamides, as described in U.S. Pat. No. 2,541,474; vinyl polymers such as described in a multiplicity of readily available U.S. Patents.

In accordance with U.S. Pat. Nos. 3,415,644, 3,415,645 and 3,415,646, an image-receiving elements need not be separated from superposed contact with a photosensitive element comprising a silver halide emulsion subsequent to substantial transfer image formation if the image-receiving element is transparent and a processing composition containing a substance rendering the processing composition layer opaque is spread between the image-receiving layer and the photosensitive element. The use of hydratable, metal-free interlayers of the present invention is considered applicable to such processes.

Specifically, an integral diffusion transfer photographic film unit particularly adapted for the production of a dye transfer image of improved stability will be constructed, for example, in accordance with aforementioned U.S. Pat. No. 3,415,644 to include a photosensitive element comprising a laminate having in sequence as essential layers, a dimensionally stable opaque support layer, a photosensitive silver halide emulsion layer having associated therewith dye image-providing material which is soluble and diffusible in alkali at a first pfi, an alkaline solution permeable polymeric layer dyeable by the dye image-providing material, a polymeric acid layer containing sufficient acidifying material to effect reduction subsequent to substantial transfer dye image formation of a processing solution having the first pH to a second pH at which said dye image-providing material is insoluble and nondiffusible, and a dimensionally stable transparent support layer, said dimensionally stable support layers comprising extremities of the described photographic film unit composite structure. in combination with the laminate a rupturable container retaining an aqueous alkaline processing composition having the first pH and containing an opacifying agent in a quantity sufficient to mask the dye image-providing material, is fixedly positioned and extends transverse the leading edge of the laminate whereby to effect unidirectional discharge of the containers contents between the alkaline solution permeable and dyeable polymeric layer and the photosensitive silver halide emulsion layer next adjacent thereto upon application of compressive force to the container.

Employment of such film units according to the described color diffusion transfer photographic process specifically provides for the production of a highly stable color transfer image accomplished at least in part by in process adjustment of the environmental pH of the film unit from a pH at which transfer processing is operative through a pH at which dye transfer is inoperative subsequent to substantial transfer image formation. The stable color transfer image is obtained irrespective of the fact that the film unit is maintained as an integral laminate during exposure, processing, viewing and storage which transfer image exhibits the required maximum and minimum dye transfer image densities, dye saturations, hues, definition, etc. It should, however, be recognized that film units fabricated in accordance with the parameters set forth directly above specifically require the presence of the stated neutralizing component disclosed in U.S. Pat. No. 3,362,819 to effect in situ process adjustment of the film units operation pH range thereby terminating the transfer process at such time as the appropriate transfer image has been formed in the image-receiving element.

It has been disclosed in U.S. Pat. No. 3,384,483 that photographic elements having at least two adjacent dye image-forming units each of which comprise silver halide emulsion and dye developer contiguous to the silver halide emulsion may be separated by an alkali-permeable water-insoluble stratum of a polyvalent metal salt of a film-forming alkali-permeable water-soluble polymer having free carboxylic acid groups, the stratum being less permeable to dye developer in aqueous alkaline solution than the polymeric carboxylic acid used to prepare the salt stratum. The barrier effect provided by the salt stratum operates on a cross-link mechanism, i.e., polyvalent metal moieties are used to form the requisite salts by cross-linking carboxylic acid moieties of the polymeric carboxylic acid to form a stratum having a certain degree of alkali permeability and water insolubility which serves as a barrier to prevent color contamination and interdevelopment between dye image-forming units. Structurally, the cross-link configurations would be, for example,

where M is a divalent metal. The permeability, then, of the barrier disclosed in the above-mentioned U.S. Patent is directly determined by the degree of cross-link provided by the metal-cross-linked polymeric carboxylic acid stratum.

it will be recognized that in contradistinction to the disclosure of the next above-denoted patent, the interlayer of the present invention is metal-free, that is, it does not depend upon metal complexing of polymeric constituents to provide the desired effect; is preferably substantially uncross-linked, that is, there is no reliance on cross-linking to provide the functionality of the present invention; and is preferably waterinsoluble. It will be patently evident, therefore, that the polymeric interlayer of the present invention which is metalfree, preferably substantially uncross-linked and water-insoluble provides a diffusion control mechanism both functionally and structurally dissimilar from that described in U.S. Pat. No. 3,384,483.

lt has now been discovered that if one or more of the interlayers of the integral multilayer photosensitive element, described above, is specifically selected to comprise a processing composition permeable and hydratable metal-free synthetic polymer having a dye-permeable lattice, that is, which is permeable to dye image-forming materials substantially only in the hydrated state, and a hydration rate less than the development and greater than the fogging rates of the dye associated silver halide next adjacent the photosensitive element's film base, significant improvement may be achieved with respect to the element's color isolation and potential photographic process speed, and with respect to the brilliance, density and hue of the transfer image color characteristics. in addition to being metal-free, the denoted polymer will preferably be substantially uncross-linked.

Specifically, employment of the detailed polymeric interlayer, during the hereinbefore described diffusion transfer process, acts to provide a barrier with respect to retardation of the positional displacement of the dye prior to establishment of substantial imagewise emulsion control of the associated dyes diffusion, with the concomitant results of providing significantly higher process speed, higher transfer image maximum densities, greater cyan and magenta dye saturation, and improved red and blue hues, in addition to, and by reason of, improved photosensitive element interimage effects. These effects result, at least in part, from prevention of the respective dyes development of silver halide emulsion strata, other than the specific strata with which the individual dye is directly associated; generally characterized, respectively, as yellow, magenta, and cyan drop-off".

The hydration with which the present system is directly concerned comprises, in general, the polymer's assimilation of water molecules by hydrogen bonding with its correlated concomitant swelling. It will also be recognized that in a given instance, the hydration and permeation of a selected specific polymer, within the photographic system context detailed, will be influenced and modulated by the polymer's relative hydrolysis, salt formation, solubility, and the like, properties.

It will accordingly be recognized, therefore, that for purposes of the instant invention the hydratable metal-free synthetic polymers disclosed possess the intrinsic capability to combine with water to provide a stratum which is, in its hydrated or combined state, permeable to material to which it is impermeable in its anhydrous condition. Further, within the context of the present invention it will be appreciated that the polymeric barrier material disclosed is permeable to alkali so that development of the photographic system may be initiated immediately, but due to the relatively large size of dye molecules, image-forming dye may not penetrate the barrier until it has achieved a hydrated condition. it will be evident that color contamination of systems utilizing the barriers disclosed and claimed herein will be substantially obviated since the release of image-forming dye is postponed until substantially complete development of the dye associated silver halide emulsion has been achieved. The obviation of premature dye penetration produces high fidelity color isolation which is not only technologically advantageous but is aesthetically pleasmg.

Image-forming dye associated with the silver halide emulsions of the present invention is held immobile by the disclosed barrier material until the silver halide emulsion having the slowest development rate is substantially developed. However, diffusion through said barrier material is not held up so long that the silver halide emulsion having the fastest development rate will fog thereby preventing image-forming dye from reaching the image-receiving element. Under ideal conditions parameters for hydration and/or development of adjacent silver halide emulsions may be determined using conventional techniques. However, it is to be emphasized that in any system utilizing the present invention, the paramount consideration is balancing the relativity of the hydration rate of the barrier material to the development and fogging rates of the related silver halide emulsions. Absolute numbers may only be used to describe one given system. Broadly speaking one of ordinary skill in the art possessing the present invention would be able to determine the specific parameters which must be utilized in designing the barrier material of the present invention when the fogging and development rates of the associated silver halide emulsions are known.

With specific regard to selection of polymers particularly adapted for employment in accordance with the instant invention, the respective rates of silver halide emulsion development, polymer hydration, and/or silver halide emulsion fogging may be directly measured, in accordance with any of the conventional techniques known in the art. Included among such techniques are procedures well known for the simultaneous derivation of both the development and fogging rate of a silver halide emulsion, by contemporaneous measurement of silver developed, per unit time, in exposed and unexposed portions of an emulsion stratum. However, a particularly apt and simple empirical method of initially determining the effective ness of a selected hydratable polymer, within the context of its ultimate photographic employment, has been found to comprise the rapid and simple procedure of microtoming a micron cross section of the integral multilayer structure, mounting same on a microscope slide which had previously been coated with a thin layer of a microscope objective immersion oil, covering the microtome section with a cover slip and including alkali solution, to the contact edge of the section, by capillary action. The effective barrier propensity of the selected polymer may then be visually recorded and corre' lated timewise with respect to development of the photosensitive emulsion strata.

The fogging rate of the silver halide emulsions employed may be suitably modulated by incorporation of a conventional antifoggant, such as those hereinbefore detailed, in the emulsion layer itself and/or associated layers and/or processing composition, and permeation of such agent, or agents, into the respective emulsion layer to be controlled.

In a preferred embodiment of the present invention, the gelatino silver halide emulsion layers are about 0.6 to 6 microns thick, the gelatino dye-retaining layers are about 1 to 7 microns thick, and the polymer interlayers are l to 5 microns thick. With respect to a preferred image-receiving element, the image-receiving layer is about 0.25 to 0.4 mil. thick, the polymeric acid layer is about 0.3 to 1.5 mils. thick, and the spacer layer is about 0.1 to 0.7 mil. thick. It will be specifically recognized that the relative dimensions recited above may be appropriately modified, in accordance with the desires of the operator, with respect to the specific product to be ultimately prepared.

The instant invention is thus directly concerned with a photosensitive element which comprises a common support having, positioned on one surface, at least two selectively sensitized photosensitive silver halide emulsion strata, for example, having predominant spectral sensitivity to separate regions of the spectrum, each having a dye of predetermined color associated therewith, for example, a spectral absorption range substantially complimentary to the predominant sensitivity range of the associated emulsion, subsequent to processing, separated by a spacer or interlayer comprising the aforementioned hydratable polymer alone or in combination with one or more additional polymers, such as gelatin, polyvinyl alcohol, and the like, and retaining photographic processing adjuncts where desired.

Preferably, however, the selected polymer is aqueous alkaline solution permeable and hydratable; most preferably, substantially instantaneously permeable by solution retained molecules having a geometric size less than the geometric size of the transfer image-forming dye, such as, for example, auxiliary silver halide developing agents, antifoggants, accelerators, arrestors, and the like, in order that photographic development, and the like, may proceed, with respect to the emulsion next adjacent the film base, within the earliest time sequence possible.

in a preferred embodiment, the selected hydratable polymer possesses a processing composition hydration rate sufficiently less than the development rate and greater than the fogging rate of the respective dye associated silver halide emulsion possessing the slowest development rate and the most rapid fogging rate of the two emulsions intermediate which the polymer is positioned; in order to simultaneously retard rearward diffusion of the dye associated with the silver halide emulsion next adjacent the elements surface and forward diffusion of the dye associated with the silver halide emulsion nert adjacent the film base, until the respective imagewise emulsion development and control of each dye is substantially established. There is thus provided an effective restriction of each dyes developing function to the specific silver halide emulsion with which is is associated, and thereby color isolation selectively determined by the incident spectral energy distribution per unit area of the respective photoresponsive silver halide emulsions exposure.

ill

As examples of aqueous alkaline solution hydratable polymers, particularly adapted for employment in accordance with the instant invention, mention maybe made of:

Vinyl acetate-crotonic acid copolymer containing less than about 5 percent crotonic acid, by weight, preferably about 1 to 3 percent crotonic acid, by weight; isopropyl cellulose, preferably containing about 1310.5 isopropyl groups per cellulosic monomer unit; hydroxypropyl methyl cellulose, preferably containing 15:0.03 methoxyl groups per cellulosic monomer unit; hydroxypropyl cellulose; acrylonitrile'acrylic acid copolymer; methyl acrylate-acrylic acid copolymer preferably containing in the order of about 3 percent by weight of acrylic acid, etc.

Other materials suitable for utilization within the environment of the present invention comprise those disclosed in US. Pat. No. 3,421,892 and include poly-N-methacrylamide; poly- N-methylmethacrylamide; poly-N'ethylacrylamide; ter polymers of N-ethylacrylamide, N-methyl-acrylamide, and acrylamide; copolymers of N-ethylacrylamide and 2-vinylpyridine; copolymers of N-isopropylacrylamide and dimethylaminoethylacrylate; copolymers of N- isopropylacrylamide and N-vinylpyrolidone; etc. In the most preferred embodiment of the disclosed invention the synthetic metal-free polymeric material utilized to provide barrier functionality will comprise a substantially uncross-linked water-insoluble material. Such water-insoluble materials provide an added feature in that they may be utilized in thicknesses somewhat less than similar barriers laid down of materials which are inherently water-soluble.

The present invention has been specifically found to possess certain distinct advantages, when compared with certain interlayer systems of the prior art, in order to effect processing in a stepwise, or layerwise, manner. Specifically, the prior art teaches the employment of a barrier interlayer to separate an outer emulsion layer and associated dye from an inner emulsion layer and its associated dye, in order that processing may be effected in the stepwise manner. The barrier layer comprises, in general, a polymeric layer which is permeated by the fluid processing composition at a rate sufficiently slow so as to insure that permeation of the fluid composition, from an outer emulsion layer into the next inner emulsion layer, is deferred, until processing of the outer emulsion layer is substantially complete. In general, barrier interlayers of this type comprise two distinct types. The first type comprises impermeable polymeric interlayers which possess a solution rate, upon contact with the fluid processing composition, during photographic processing, such that the interlayer requires a longer time span to be rendered permeable than the time interval necessitated to effect development of the outer emulsion stratum. The second type comprises impermeable polymeric interlayers which possess a hydrolysis rate, upon contact with the fluid processing composition, such that the interlayer requires a time interval for the occurrence of hydrolysis, suffrcient as to provide processing composition permeability, in excess of that required to effect development of the outer emulsion.

As will be appreciated from the above description of the prior art barrier interlayers, the present invention possesses, when compared with such prior art systems, the specific advantage of providing the previously stated control of dye diflu sion during substantially contemporaneous development of all the emulsion strata constituting the integral multilayer photosensitive element. It thus avoids the prior art's necessity of conducting development in relatively insulated steps, with such processesconcomitant increase in the necessary processing time interval and the resultant propensity for image degradation, for example, from fog buildup and the like, in the outer emulsion strata remaining in processing composition contact for an overly extended period, or conducting substantially contemporaneous development of all the emulsion strata, with resultant loss of color isolation, due to undesirable migration of dye preceding effective control, or an empirical system combining the above systems in such a manner as is designed to effect a balance between the undesirable effects of each and to thus minimize the effects to at least some effective extent.

In accordance with the teachings of the art, the positioning of the respective silver halide emulsion/dye developer units of the tripack configuration detailed above may be varied. However, it is generally preferred to constitute the tripak configuration in accordance with the general scheme set forth in the drawing, that is, the cyan dye developed/red-sensitive emulsion unit next contiguous the support surface and the yellow dye developer/blue-sensitive emulsion unit most distant from the support surface.

As detailed in the illustrative drawing, a selectively exposed photosensitive element 25 comprises: a support a layer 11 containing a cyan dye developer; a layer 12 comprising a redsensitive silver halide emulsion; an interlayer 13 comprising the polymer detailed above; a layer 14 containing a magenta dye developer; a layer 15 comprising a green-sensitive silver halide emulsion; an interlayer 16 comprising the polymer detailed above; a layer 17 containing a yellow dye developer; a layer 18 comprising a blue-sensitive silver halide emulsion; and a protective overcoat layer 19.

As shown in the drawing, the multilayer exposed photosensitive element 25 is shown in processing relationship with an image-receiving element 26 which, as aforenoted, may be permanently integral therewith, and a layer 20 of processing composition distributed intermediate elements and 26.

Image-receiving element 26 comprises: a support 24 which may be transparent; a neutralizing layer 23; a spacer layer 22; and an image-receiving layer 21.

As previously discussed, liquid processing composition 20 is effective to initiate development of the latent images in the respective silver halide emulsion strata and hydration of the polymeric interlayers. After a suitable imbibition period, during which at least a portion of the dye developer associated with unexposed areas of each of the emulsions is transferred to superposed image-receiving element 26, the latter element may be separated to reveal the positive multicolor image.

The present invention will be illustrated in greater detail in conjunction with the following procedures which set out representative embodiments and photographic utilization of the novel photosensitive elements of this invention, which, however, are not limited to the details therein set forth and are intended to be illustrative only.

A photosensitive element similar to that shown in the drawing was prepared by coating, in succession, on a gelatin subbed cellulose triacetate film base, the following layers;

1. a layer of the cyan dye developer 1,4-bis-(B-[hydroquinoyl-a-methyl1-ethylamino)-5,8-dihydroxy-anthraquinone dissolved in diethyl lauramide, dispersed in gelatin and coated at a coverage of 159 mgs. per square foot of dye and 119 mgs. per square foot of gelatin.

2. a red-sensitive gelatino-silver iodobromide emulsion containing 4-methylphenyl hydroquinone coated at a coverage of 222 mgs. per square foot of silver, 15 mgs. per square foot of 4'-methylphenyl hydroquinone, and l37 mgs. per square foot of gelatin;

3. a layer of vinyl acetate-crotonic acid copolymer containing 2 percent by weight, crotonic acid, coated at a coverage of I80 mgs. per square foot;

4. a layer of the magenta dye developer 2-(p-[a-hydroquinonylethyl]-phenylazo)-4-isopropoxy-l-naphthol, dissolved in diethyl lauramide, dispersed in gelatin and coated at a coverage of 65 mgs. per square foot of dye and 97 mgs. per square foot of gelatin;

5. a green-sensitive gelatino-silver iodobromide emulsion coated at a coverage of 108 mgs. per square foot of silver and 68 mgs. per square foot of gelatin;

6. a layer of gelatin coated at a coverage of 140 mgs. per square foot;

7. a layer of the yellow dye developer 4-(p-[/3 hydroguinonyethyl]-phenylazo)-3-(N-n-hexyl-carboxamido)- l-phenyl-S-pyrazolone, I dissolved in diethyl lauramide, dispersed in gelatin and coated at a coverage of 55 mgs. per square foot of dye and 69 mgs. per square foot of gelatin;

8. a blue-sensitive gelatino-silver iodobromide emulsion coated at a coverage of 6] mgs. per square foot of silver and 46 mgs. per square foot of gelatin; and

9. a layer containing 4'-methylphenyl hydroquinone dissolved in diethyl lauramide, dispersed in gelatin and coated at a coverage of 10 mgs. per square foot of 4-methylphenyl hydroquinone and 30 mgs. per square foot of gelatin.

Additional photosensitive elements substantially of the lastidentified type also were fabricated employing, as Layer 3, a mixture comprising mgs. per square foot and 10 mgs. per square foot; 1 ll mgs. per square foot and 14 mgs. per square foot; 134 mgs. per square foot and l6 mgs. per square foot; and 156 mgs. per square foot and 19 mgs. per square foot, of the identified crotonic acid copolymer and gelatin, respectively.

For purposes of comparison, a photosensitive element substantially of the last-identified type was also fabricated employing, as Layer 3, 180 mgs. per square foot of gelatin and 10 mgs. per square foot of 4-methyl-phenyl hydroquinone, the latter shifted from Layer 2. In addition, in order to optimize the control, the coverages of Layers 4 and 7 were increased by 10 percent.

The required number of image-receiving elements were prepared by coating a cellulose nitrate subcoated baryta paper with the partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high viscosity poly-(ethylene/maleic anhydride), grams of n-butyl alcohol and 1 cc. of 85 percent phosphoric acid to provide a polymeric acid layer approximately 0.75 mils. thick. The external surface of the spacer layer was then coated with a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine, at a coverage of approximately 600 mgs. per square foot, to provide a polymeric image-receiving layer approximately 0.40 mils. thick. The thus-prepared image-receiving element was then baked at F. for 30 minutes and then allowed to cool.

The photosensitive elements were then exposed and processed by spreading an aqueous liquid processing composition comprising:

Water l00 cc.

Potassium hydroxide l 1.2 g. Hydroxyethyl cellulose (high viscosity) [commercially available from Hercules Powder Co., Wilmington 99, Del., under the trade name Natrasol 250) 3.9 g. Potassium thiosulfate 0.5 g. Benzotriazole 3.5 g. N-benzyl-a-picolinium bromide 2.0 g. Lithium Hydroxide 0.5 g.

between an individual image-receiving element and each of the exposed multicolor elements, as they were brought into superposed relationship in a Polaroid Land Camera. After an imbibition period of 1 minute, the picture door of the camera was opened and the imageqeceiving element separated from the remainder of the film assembly.

Fxamination of the resultant control and test transfer prints are summarized below:

Direct visual observation reflected improved color brilliance, hues, saturation, and isolation. Photographic and visual examination of exposed and processed photosensitive element microtome sections revealed decreased interimage effects within the processed element fabricated in accordance with the instant invention, as compared with the control element; especially noted was a substantial decrease in amount of magenta drop off."

Procedures substantially analogous to those detailed above were repeated employing the previously identified hydroxypropyl cellulose, at a coverage of 90 mgs. per square foot, and hydroxypropyl methyl cellulose, methyl acrylate-acrylic acid, acrylonitrileecrylic acid, polyvinyl hydrogen phthalate, and polyacrylic acid, at a coverage of 180 mgs. per square foot.

Of the aforementioned polymeric interlayers, the identified hydroxypropyl cellulose, methyl acrylate-acrylic acid, acrylonitrile-acrylic acid, and hydroxypropyl methyl cellulose provided results substantially identical with those detailed with respect to the employment of the designated vinyl acetatecrotonic acid copolymer. However, polyvinyl hydrogen phthalate and polyacrylic acid provided a hydration rate more rapid than the development rate of the respective silver halide emulsion strata next adjacent the support and, as a result, failed to provide the advantageous results detailed above.

Furthermore, procedures substantially analogous to those detailed above were repeated employing certain of the barrier materials disclosed and claimed in above-denoted U.S. Pat. No. 3,421,892 which comprised substituting for Layer 3 in the structure substantially as denoted above: (a) a layer ofpoly-N- isopropylacrylamide coated at a coverage of 30 mgs. per square foot; (6) a layer of poly-N-ethylacrylamide coated at a coverage of H mg. per square foot; and (c) a layer comprising a l-l9 copolymer of bl,l l-(,B-dimethylamino)ethylacrylamide and N-isopropylacrylamide containing 2 percent of polyacrylamide.

The following table denotes the results achieved. It should be noted that, in contradistinction to the above-designated table, the dye densities reported herein are differential dye densities, i.e., maximum dye densities minus stain (D,,,,,,.D,,,,,).

mide with 2% polyacrylamide The above table is couched in terms of differential dye densities rather than maximum densities since the experimental information was recorded in this manner. Even though the dye densities reported are diminished by the stain or D,,,,,, present, it will be recognized that substantially better results are obtained with the denoted compositions than with the gelatin control reported further above.

it will be noted that the liquid processing composition employed may contain an auxiliary or accelerating developing agent, such as p-methylaminophenol, 2,4-diamino-phenol, pbenzylaminophenol, hydroquinone, toluhydroquinine, phenylhydroquinone, 4'-methylphenylhydroquinone, etc. It is also contemplated to employ a plurality of auxiliary or accelerating developing agents, such as 3-pyrazolidone developing agent and a benzenoid developing agent, as disclosed in U.S. Pat. No. 3,039,869, issued June 19, 1962. As examples of suitable combinations of auxiliary developing agents, mention may be made of l-phenyl-ii-pyrazolidone in combination with pbenzylaminophenol and l-phenyl-3-pyrazolidone in combination with 2,5-bis-ethyleneimino hydroquinone. Such auxiliary lid developing agents may be employed in the liquid processing composition or they may be initially incorporated, at least in part, in any one or more of the silver halide emulsion strata, the strata containing the dye developers, the interlayers, the overcoat layer, the image-receiving layer, or in any other auxiliary layer, or layers, of the film unit. It may be noted that at least a portion of the dye developer oxidized during development may be oxidized and immobilized as a result of a reaction, e.g., an energy-transfer reaction, with the oxidation product of an oxidized auxiliary developing agent, the latter developing agent being oxidized by the development of exposed silver halide. Such a reaction of oxidized developing agent with unoxidized dye developer would regenerate the auxiliary developing agent for further reaction with the exposed silver halide.

In addition, development may be effected in the presence of an onium compound, particularly a quaternary ammonium compound, in accordance with the process disclosed in U.S. Pat. No. 3,173,786.

Although the invention has been discussed in detail throughout employing dye developers, the preferred dye image-forming materials, it will be readily recognized that other, less preferred, dye image-providing materials may be substituted in replacement of the preferred dye developers in the practice of the invention. For example, there may be em ployed dye image-forming materials such as those disclosed in U.S. Pat. Nos. 2,647,049, issued July 28, 1953; 2,661,293, issued Dec. 1, 1953; 2,698,244, issued Dec. 28, 1954; 2,698,798, issued Jan. 4, i955; and 2,802,735, issued Aug. 13, 1957, wherein color diffusion transfer processes are described which employ color coupling techniques comprising, at least in part, reacting one or more color developing agents and one or more color formers or couplers to provide a dye transfer image to a superposed image-receiving layer and those disclosed in U.S. Pat. No. 2,774,668, issued Dec. 18, 1956, wherein color diffusion transfer processes are described which employ the imagewise differential transfer or complete dyes by the mechanisms therein described to provide a transfer dye image to a contiguous image-receiving layer.

In products employed in the diffusion transfer processes of this invention, it may be preferable to expose from the emulsion side. In such instances, it is, therefore, desirable to hold the photosensitive element and the image-receiving element together at one end thereof by suitable fastening means in such manner that the photosensitive element and the imagereceiving element may be spread apart from their superposed processing position during exposure. A camera apparatus suitable for processing film of the type just mentioned is provided by the Polaroid Land Camera, sold by Polaroid Corporation, Cambridge, Mass, or similar camera structure such, for example, as the roll film type camera forming the subject matter of U.S. Pat. No. 2,435,717 or the film pack type camera forming the subject matter of U.S. Pat. No. 2,991,702. Camera apparatus of this type permits successive exposure of individual frames of the photosensitive element from the emulsion side thereof as well as individual processing of an exposed frame by bringing said exposed frame into superposed relation with a predetermined portion of the image-receiving element while drawing those portions of the film assembly between a pair of pressure rollers which require a container associated therewith and effect the spreading of the processing liquid released by rupture of said container, between and in contact with exposed photosensitive frame and the predetermined, registered area of the image-receiving element.

it will be apparent that the relative proportions of the agents of the diffusion transfer processing composition may be altered to suit the requirements of the operator. Thus, it is within the scope of this invention "to modify the herein described developing compositions by the substitution of preservatives, allralies, silver halide solvents, etc., other than those specifically mentioned, provided that the pH of the composition is preferably in excess of at least 10 initially. When desirable, it is also contemplated to include, in the developing composition, components such as restrainers, accelerators, etc. Similarly, the concentration of various components may be varied over a wide range and when desirable adaptable components may be disposed in the photosensitive element, prior to exposure, in a separate permeable layer of the photosensitive element and/or in the photosensitive emulsion.

The support layers referred to may comprise any of the various types of conventional rigid or flexible supports, for example, glass, paper, metal, and polymeric films of both synthetic types and those derived from naturally occurring products. Suitable materials include paper; aluminum; polymethacrylic acid methyl and ethyl esters; vinyl chloride polymers; polyvinyl acetal; polyamides such as nylon; polyesters such as polymeric films derived from ethylene glycol terephthalic acid; and cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate, butyrate, acetatepropionate, or acetate-butyrate.

The nature and construction of rupturable containers is well understood in the art; see, for example, US. Pat. No. 2,543,181, issued Feb. 27, 1951, and US. Pat. No. 2,634,886, issued Apr. 14, 1953.

It will be further apparent that, by appropriate selection of the image-receiving element materials from among suitable known opaque and transparent materials, it is possible to obtain either a colored positive reflection print or a colored positive transparency.

While a rupturable container provides a convenient means for spreading a liquid processing composition between layers of film unit whereby to permit the processing to be carried out within a camera apparatus, the practices of this invention may be otherwise effected. For example, a photosensitive element, after exposure in suitable apparatus and while preventing further exposure thereafter to actinic light, may be removed from such apparatus and permeated with the liquid processing composition, as by coating the composition on said photosensitive element or otherwise wetting said element with the composition, following which the permeated, exposed photosensitive element, still, without additional exposure to actinic light, is brought into contact with the image-receiving element for image formation in the manner heretofore described.

In all examples of this specification, percentages of components are given by weight unless otherwise indicated.

Throughout the specification and appended claims, the expression positive image has been used. This expression should not be interpreted in a restrictive sense since it is used primarily for purposes of illustration, in that it defines the image produced on the image-carrying layer as being reversed, in the positive-negative sense, with respect to the image in the photosensitive element. As an example of an alternative meaning for positive image," assume that the photosensitive element is exposed to actiriic light through a negative transparency. In this case, the latent image in the photosensitive element will be a positive and the image produced on the image-carrying layer will be a negative. The

expression positive image is intended to cover such an image produced on the image-carrying layer.

Throughout the specification and claims, the expression superposed has been used. This expression is intended to cover the arrangement of two layers in overlying relation to each other either in face-to-face contact or in separated condition and including between them at least a layer of fluid processing composition.

It also will be recognized that, where desired, the film unit structure may also comprise an integral positive/negative construction carried on a single support.

In the preferred embodiments of the present invention, the polymeric interlayer preferably has a measured thickness not less than 20 percent and not exceeding twice the thickness and coverage of the silver halide emulsion stratum next adjacent the support.

In addition to the described essential layers, it will be recognized that the film unit may also contain one or more subcoats or layers, which, in turn, may contain one or more additives such as plasticizers, intermediate essential layers for the purpose, for example, of improving adhesion.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A photosensitive element which comprises, in combination:

a. a support layer;

b. at least two selectively sensitized silver halide emulsion layers, each having associated therewith a dye imageforrning material of predetermined color; and a layer intermediate said emulsion layers comprising an alkaline processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming material only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye imageforming materials subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said intermediate layer and resultant diffusion of dye image-forming materials therethrough.

2. The invention of claim I wherein at least one of said dyes is disposed in a separate layer adjacent its associated silver halide emulsion.

3. The invention of claim 2 wherein said separate layer comprises gelatin.

4. The invention of claim 1 wherein said hydratable synthetic polymer is selected from the group consisting of cellulosic and vinyl polymers.

5. The invention of claim 1 wherein said hydratable synthetic polymer is substantially uncross-linked.

6. The invention of claim 1 wherein said hydratable synthetic polymer is substantially water-insoluble.

7. The invention of claim 1 wherein said hydratable synthetic polymer comprises a vinyl acetate-crotonic acid copolymer having less than 5 percent crotonic acid by weight.

8. The invention of claim 1 wherein said hydratable synthetic polymer comprises hydroxypropyl cellulose.

9. The invention of claim 1 wherein said hydratable synthetic polymer comprises hydroxypropyl methyl cellulose.

10. A photographic film unit which comprises, in combination:

a photosensitive element having a diffusion transfer imagereceiving element affixed at least one edge thereof, said photosensitive element comprising as essential layers:

a. a support layer;

b. at least two selectively sensitized silver halide emulsion layers each having a dye which is a silver halide developing agent of predetermined color associated therewith; and a layer intermediate at least two of said silver halide emulsion layers comprising an alkaline processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming material only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye image-forming subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said intermediate layer and resultant diffusion of dye image-forming materials therethrough, said diffusion transfer imagereceiving element comprising as essential layers, in sequence:

d. a support layer; and I e. an alkaline processing composition permeable and dyeable polymeric layer; wherein said photosensitive and said image-receiving elements are adapted to be superposed, the support layers of each comprising the extremities of the superposed structure.

llll. The invention of claim wherein said image receiving element additionally comprises a polymeric acid layer intermediate the support layer and dyeable polymeric layer.

112. The invention of claim 10 including a rupturable container retaining an aqueous alkaline processing solution affixed one edge of said photosensitive and said image-receiving elements and adapted upon rupture to distribute the contents intermediate said photosensitive element and said imagereceiving element.

H3. The invention of claim 12 wherein said aqueous alkaline processing solution has a pH of not less than about 12.

lid. The invention of claim 112 wherein said image-receiving element support layer is transparent.

15. The invention of claim 114 wherein said photographic film unit comprises a composite structure comprising said photosensitive element and said image-receiving element permanently affixed each to the other in superposed relationship, the support layers of each of said elements comprising the extremities of said composite structure.

16. The invention of claim 1110 which comprises, in combination:

a photosensitive element containing a plurality of essential layers including in sequence;

a. a support layer;

b. a cyan dye containing layer associated with a red-sensitive silver halide emulsion;

c. a spacer layer;

d. a magenta dye containing layer associated with a greensensitive silver halide emulsion;

e. a spacer layer; and

f. a yellow dye containing layer associated with a blue-sensitive silver halide emulsion;

each of said cyan, magenta and yellow dyes being silver halide developing agents and at least one of said spacer layers comprising a processing solution permeable and hydratable metalfree synthetic polymer, which is permeable to dye imageforming materials only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye image-forming materials subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said processing solution permeable and hydratable synthetic polymeric spacer layer and resultant diffusion of dye image-forming materials therethrough.

H7. The invention of claim 16 wherein said hydratable synthetic polymer is selected from the group consisting of cellulosic and vinyl polymers.

lid. The invention of claim 16 wherein said hydratable synthetic polymer is substantially uncross-linked.

119. The invention of claim 16 wherein said hydratable synthetic polymer is substantially water-insoluble.

20. A process for forming transfer images in color which comprises the steps of:

exposing a photosensitive element comprising at least two selectively sensitized silver halide emulsion layers, each having associated therewith a dye image-forming material of predetermined color, said material additionally being a silver halide developing agent, and a layer intermediate at least two of said silver halide emulsion layers comprising an aqueous alkaline processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming material only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye image-forming materials subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said intermediate layer and resultant diffusion of dye image-forming materials therethrough;

contacting said exposed photosensitive element with said aqueous alkaline processing composition affecting thereby substantially concomitant development of said silver halide emulsions and hydration of said alkaline solution permeable and hydratable polymer whereby dye associated with each of said emulsions is immobilized as a result of development thereby forming imagewise distributions of mobile dye as a function of the point-topoint degree of exposure thereof; and

transferring by diffusion at least a portion of each of said imagewise distributions of mobile dye to a superposed image-receiving layer to provide: thereto a multicolored dye image. 211. The invention of claim 20 wherein said hydratable synthetic polymer is selected from the group consisting of vinyl and cellulosic polymers.

22. The invention of claim 20 wherein said hydratable synthetic polymer is substantially uncross-linked.

23. The invention of claim 20 wherein said hydratable synthetic polymer is substantially water-insoluble.

241. The invention of claim 21 wherein said synthetic polymer comprises a vinyl acetate-crotonic acid copolymer having less than 5 percent crotonic acid by weight.

25. The invention of claim 21 wherein said polymer comprises hydroxypropyl cellulose.

26. The invention of claim 21 wherein said polymer comprises hydroxypropyl methyl cellulose.

27. The invention ofclaim 20 which comprises the steps of: exposing a photosensitive element which comprises bluesensitive, green-sensitive and red-sensitive silver halide emulsion layers mounted on a common support, said blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers having associated therewith, respectively, yellow, magenta and cyan dyes, each of said dyes being a silver halide developing agent, at least two of said emulsions and associated dyes having interposed therebetween a layer comprising an aqueous alkaline processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming material only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye image-forming materials subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding; substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said interposed layer and resultant diffusion of dye image-forming materials therethrough;

applying said aqueous alkaline processing solution to said exposed photosensitive element thereby initiating development of said photosensitive emulsion layers and hydration of said hydratable synthetic polymer, immobilizing said yellow, magenta and cyan dyes as a result of development of the exposed areas of their associated silver halide emulsions forming thereby an imagewise distribution of mobile yellow, magenta and cyan dyes in unexposed areas of their associated emulsions as a function of the point-to-point degree of exposure; and

synthetic polymer is substantially water-insoluble.

31. The invention of claim 27 wherein the support layer for said image-receiving element is transparent.

32. The invention of claim 31 wherein said photosensitive element and said image-receiving element are permanently affixed each to the other in superposed relationship thereby forming a composite structure. the support layers of each of said elements comprising the extremities of said structure.

l U i i i 

2. The invention of claim 1 wherein at least one of said dyes is disposed in a separate layer adjacent its associated silver halide emulsion.
 3. The invention of claim 2 wherein said separate layer comprises gelatin.
 4. The invention of claim 1 wherein said hydratable synthetic polymer is selected from the group consisting of cellulosic and vinyl polymers.
 5. The invention of claim 1 wherein said hydratable synthetic polymer is substantially uncross-linked.
 6. The invention of claim 1 wherein said hydratable synthetic polymer is substantially water-insoluble.
 7. The invention of claim 1 wherein said hydratable synthetic polymer comprises a vinyl acetate-crotonic acid copolymer having less than 5 percent crotonic acid by weight.
 8. The invention of claim 1 wherein said hydratable synthetic polymer comprises hydroxypropyl cellulose.
 9. The invention of claim 1 wherein said hydratable synthetic polymer comprises hydroxypropyl methyl cellulose.
 10. A photographic film unit which comprises, in combination: a photosensitive element having a diffusion transfer image-receiving element affixed at least one edge thereof, said photosensitive element comprisIng as essential layers: a. a support layer; b. at least two selectively sensitized silver halide emulsion layers each having a dye which is a silver halide developing agent of predetermined color associated therewith; and c. a layer intermediate at least two of said silver halide emulsion layers comprising an alkaline processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming material only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye image-forming subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said intermediate layer and resultant diffusion of dye image-forming materials therethrough, said diffusion transfer image-receiving element comprising as essential layers, in sequence: d. a support layer; and e. an alkaline processing composition permeable and dyeable polymeric layer; wherein said photosensitive and said image-receiving elements are adapted to be superposed, the support layers of each comprising the extremities of the superposed structure.
 11. The invention of claim 10 wherein said image-receiving element additionally comprises a polymeric acid layer intermediate the support layer and dyeable polymeric layer.
 12. The invention of claim 10 including a rupturable container retaining an aqueous alkaline processing solution affixed one edge of said photosensitive and said image-receiving elements and adapted upon rupture to distribute the contents intermediate said photosensitive element and said image-receiving element.
 13. The invention of claim 12 wherein said aqueous alkaline processing solution has a pH of not less than about
 12. 14. The invention of claim 12 wherein said image-receiving element support layer is transparent.
 15. The invention of claim 14 wherein said photographic film unit comprises a composite structure comprising said photosensitive element and said image-receiving element permanently affixed each to the other in superposed relationship, the support layers of each of said elements comprising the extremities of said composite structure.
 16. The invention of claim 10 which comprises, in combination: a photosensitive element containing a plurality of essential layers including in sequence; a. a support layer; b. a cyan dye containing layer associated with a red-sensitive silver halide emulsion; c. a spacer layer; d. a magenta dye containing layer associated with a green-sensitive silver halide emulsion; e. a spacer layer; and f. a yellow dye containing layer associated with a blue-sensitive silver halide emulsion; each of said cyan, magenta and yellow dyes being silver halide developing agents and at least one of said spacer layers comprising a processing solution permeable and hydratable metal-free synthetic polymer, which is permeable to dye image-forming materials only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye image-forming materials subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said processing solution permeable and hydratable synthetic polymeric spacer layer and resultant diffusion of dye image-forming materials therethrough.
 17. The invention of claim 16 wherein said hydratable synthetic polymer is selected from the group consistiNg of cellulosic and vinyl polymers.
 18. The invention of claim 16 wherein said hydratable synthetic polymer is substantially uncross-linked.
 19. The invention of claim 16 wherein said hydratable synthetic polymer is substantially water-insoluble.
 20. A process for forming transfer images in color which comprises the steps of: exposing a photosensitive element comprising at least two selectively sensitized silver halide emulsion layers, each having associated therewith a dye image-forming material of predetermined color, said material additionally being a silver halide developing agent, and a layer intermediate at least two of said silver halide emulsion layers comprising an aqueous alkaline processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming material only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye image-forming materials subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said intermediate layer and resultant diffusion of dye image-forming materials therethrough; contacting said exposed photosensitive element with said aqueous alkaline processing composition affecting thereby substantially concomitant development of said silver halide emulsions and hydration of said alkaline solution permeable and hydratable polymer whereby dye associated with each of said emulsions is immobilized as a result of development thereby forming imagewise distributions of mobile dye as a function of the point-to-point degree of exposure thereof; and transferring by diffusion at least a portion of each of said imagewise distributions of mobile dye to a superposed image-receiving layer to provide thereto a multicolored dye image.
 21. The invention of claim 20 wherein said hydratable synthetic polymer is selected from the group consisting of vinyl and cellulosic polymers.
 22. The invention of claim 20 wherein said hydratable synthetic polymer is substantially uncross-linked.
 23. The invention of claim 20 wherein said hydratable synthetic polymer is substantially water-insoluble.
 24. The invention of claim 21 wherein said synthetic polymer comprises a vinyl acetate-crotonic acid copolymer having less than 5 percent crotonic acid by weight.
 25. The invention of claim 21 wherein said polymer comprises hydroxypropyl cellulose.
 26. The invention of claim 21 wherein said polymer comprises hydroxypropyl methyl cellulose.
 27. The invention of claim 20 which comprises the steps of: exposing a photosensitive element which comprises blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers mounted on a common support, said blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers having associated therewith, respectively, yellow, magenta and cyan dyes, each of said dyes being a silver halide developing agent, at least two of said emulsions and associated dyes having interposed therebetween a layer comprising an aqueous alkaline processing solution permeable and hydratable metal-free synthetic polymer which is permeable to dye image-forming material only in the hydrated state and is processing solution hydratable at a rate which renders said synthetic polymer layer permeable to dye image-forming materials subsequent to substantial development of the dye associated silver halide emulsion possessing the slowest development rate and preceding substantial fogging of the dye associated silver halide emulsion possessing the most rapid fogging rate so that substantial development of said silver halide emulsions is accomplished prior to substantial hydration of said inteRposed layer and resultant diffusion of dye image-forming materials therethrough; applying said aqueous alkaline processing solution to said exposed photosensitive element thereby initiating development of said photosensitive emulsion layers and hydration of said hydratable synthetic polymer, immobilizing said yellow, magenta and cyan dyes as a result of development of the exposed areas of their associated silver halide emulsions forming thereby an imagewise distribution of mobile yellow, magenta and cyan dyes in unexposed areas of their associated emulsions as a function of the point-to-point degree of exposure; and transferring by diffusion at least a portion of each of said imagewise distributions of dye to a superposed image-receiving layer to provide thereto a multicolor dye image.
 28. The invention of claim 27 wherein said hydratable synthetic polymer is selected from the group consisting of cellulosic and vinyl polymers.
 29. The invention of claim 27 wherein said hydratable synthetic polymer is substantially uncross-linked.
 30. The invention of claim 27 wherein said hydratable synthetic polymer is substantially water-insoluble.
 31. The invention of claim 27 wherein the support layer for said image-receiving element is transparent.
 32. The invention of claim 31 wherein said photosensitive element and said image-receiving element are permanently affixed each to the other in superposed relationship thereby forming a composite structure, the support layers of each of said elements comprising the extremities of said structure. 